CHAPTER XXVIII 



CULVERTS AND BRIDGES 



Importance of Culverts and Bridges. A large proportion 

 of the cost of maintaining the highways of the country is 

 used in the construction of culverts and bridges. Not only 

 is it desirable that the money thus expended be used in such 

 a way as to secure the best results, but faulty construction 

 should be guarded against on account of the risk of life to 

 those who must pass over them with heavy loads. To 

 secure economy it is necessary that bridges and culverts be 

 intelligently and economically designed, and that they be 

 made of durable and permanent material. Recent changes 

 in road traffic demand that there shall be advancement in 

 the designing and constructing of culverts and bridges, in 

 order that the heavier loads which bridges are now called 

 upon to bear shall be carried without risk of failure. 



Design of Culverts and Bridges. The designing of cul- 

 verts and bridges should be placed in the hands of a skilled 

 engineer, who will be able to proportion the structure 

 properly. The practice in certain localities of making appro- 

 priations of public funds for bridges without first securing 

 from one who has had experience an estimate of the cost of a 

 bridge to fill the requirements of the conditions to be met 

 may be justly criticised. 



Size. The first feature in the consideration of a culvert 

 is the determination of the size required. Highway engineers 

 have reported that culverts are often not properly propor- 

 tioned to the needs to be met, being either too large or too 

 small. The area of a cross-section of a culvert or bridge 



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